Final answer:
The process where sounds in a word change to be more similar to neighboring sounds, as in the pronunciation of /kwin/ for "queen" becoming [kin] and /vækjūm/ for "vacuum" becoming [vækūm], is called assimilation.
Step-by-step explanation:
The pronunciation of /kwin/ becoming [kin] for "queen" and /vækjūm/ becoming [vækūm] for "vacuum" are examples of assimilation. Assimilation is a phonological process where a sound changes to be more like a neighboring sound. This makes it easier to articulate the words quickly. In the case of "queen", the /w/ sound influences the /k/ sound and results in it being dropped, making the pronunciation [kin]. Similarly, for "vacuum", the /j/ sound between the two vowels is dropped for ease of pronunciation, generating [vækūm].